The present invention relates to a hydrometallurgical method for recovery of metals and/or semimetals from waste materials containing compound semiconductor materials and/or back contact materials and/or transparent electrically conducting oxides (TCO's) and therefore a wet chemical method for recovery of metals, which often occur only in low concentration, inter alia, as typical III-V, II-VI, or I-II-VI2 compound semiconductor materials in high-tech or green-tech wastes, or electrical and electronic wastes, but also as back contacts, such as molybdenum, or as front contacts, such as TCO's (transparent, electrically conductive oxides). Without elements such as indium, gallium, arsenic, cadmium, tellurium, molybdenum, copper, silver, and selenium, for example, photovoltaic plants, modern Tablet PCs, and smart phones are not conceivable, wherein the listed metals are often processed as intermediates, for example, as gallium arsenide (GaAs) and thus have completely different properties than displayed by the elements of which they consist. For this variety of materials, which are essential for our present innovative products, there is not yet a universal solution relating to the recovery of production wastes and end-of-life products. In addition to silicon-based photovoltaic technologies, there are presently a variety of other PV wastes, based on thin-film technologies using copper-indium-diselenide (CIS), copper-indium-gallium-diselenide (GIGS), cadmium telluride (CdTe), and gallium arsenide (GaAs). The economic significance of the recycling of PV modules and the renewed use linked thereto of these materials has become an important theme in the meantime.
However, the dissipative use of many special materials in countless products (thin-film photovoltaic modules, mobile telephones, flat screen displays, etc.) makes recycling more difficult and only permits recovery in recycling loops up to a certain degree. Focusing on included valuable metals all too often rapidly has the result that the processing thereof may not be performed cost-effectively, in particular because a specific introduction of energy having corresponding costs is presently to be taken into consideration. However, if synergies are included, universal methods are applied, and an attempt is made for a recovery method which can convert every component of the respective waste into products as much as possible, there are good chances for establishing economically successful recycling.
In addition, official regulations, for example, the new German “Law on Life-Cycle Management” are often applied to a maximum quota for the recycling—in the case of a minimum usage of resources (for example, energy and raw materials). Furthermore, new guidelines are being worked on all over Europe for high-tech and green tech products, such as the compulsory guidelines of the European Parliament and directive on waste electrical and electronic equipment (WEEE directive). These comprehensively regulate the correct recycling of waste electrical and electronic equipment, including the financing thereof by the producers—and in future also the recycling of photovoltaic modules.
In addition, interest in cost-effective recycling methods has been generated from these developments.
With regard to the eco-toxicity of the participating materials, it is noteworthy that toxic elements, such as arsenic or cadmium, play a significant role both in PV modules and also in communication equipment.
It is all the more important to offer environmentally-friendly recycling methods for production wastes or defective or discarded products, which is the goal of the present invention.
Presently, cadmium-telluride waste is processed in the USA and Malaysia, wherein the method is described as very complex (U.S. Pat. No. 5,453,111). The skimming off of plastic after a hot nitric acid treatment of pulverized modules does not represent a good economic and ecological solution. Thermal treatment (pyrolysis) and the removal of some metals in the gas phase (EP 1187224 B1) also will not result in a cost-effective method. A method for reclaiming exclusively cadmium and tellurium is described in U.S. Pat. No. 6,391,165 B1, while German patent specification DE 102008058530 before only deals with so-called chalcopyrites. All of these processes are only directed to individual semiconductor types in each case and exclusively treat photovoltaic materials. A recycling option for wastes containing gallium-arsenide has heretofore been completely lacking.